Normal fuel control with acceleration override control for gas turbine engine



Feb. 20, 1962 H. c. zElsLol-T 3,021,674

NORMAL FUEL CONTROL WITH ACCELERATION VERRIDE CONTROL FOR GAS TURBINEENGINE Filed Jan. 3l, 1955 I 2804?#230 j Gov ma@ www ZKM/MQW TMA/ff3,921,674 NRMAL FUEL CUNTRL WillH ACCEEERATEN VER; TEE CNTRL EUR GASTURBNE ENGNE Harry C. Zeisloft, Rochester, NX., assignor to The BendixCorporation, a corporation of Delaware Fiied Jan. 31, 1955, Ser. No.485,226 iti @latinsa (Ci. 6ft- $9.23)

This invention relates to a fuel feeding device for combustion enginesand more particularly to speed governing mechanism therefor; it has beenfound to be most particularly adapted for use with combustion engines ofthe gas turbine type.

t is common practice to utilize centrifugal governing mechanism of themechanical iiy-Weight type to control a fuel metering or throttle valvein fuel control systems for gas turbine engines, the governing mechanismincluding a governor spring which is normally manually adjustable by thepilot to accelerate and decelerate the engine to a selected speed.

The most widely used type of governing mechanism for gas turbine engineshas been the so-called proportional type, wherein any deviation inengine speed from an equilibrium setting or operating condition resultsin a fuel now correcting opening or closing movement of the throttlevalve which is proportional to the speed deviation. One of the primaryadvantages of this type of governor as compared, for example, with anisochronous or non-speed deviating type, relates to the fact that theabove noted proportional action results in engine operating stability,since tl e valve does not travel to a fully open or fully closedposition whenever a slight deviation in engine speed occurs, withsubsequent hunting for an equilibrium location.

Heretofore, proportional type governors for gas turbine engines havebeen Classifiable in two main groups, viz. the direct acting kind inwhich the fly weights and govrnor spring act directly on the throttlevalve, and the servo actuated type in which the governing mechanismfunctions through a power boost travel type servo device to control theposition of the valve. The former type is well illustrated in the MockPatent No. 2,689,606, led December 13, i945, and the latter type in thecopending application of Andrew A. Kuzmitz Serial No. 446,335, tiledIuiy 28, 1954 (common assignee), now abandoned.

One of the disadvantages of both f the above mentioned classes ofproportional type governors is that maximum throttle valve travel islimited by the amount of displacement which can be imparted thereto bythe movement of the centrifugal weights, either directly, as in the Mockpatent, supra, or through servo mechanism, as in the Kuzmitzapplication, supra. Y

My invention overcomes this disadvantage by providing a servo poweredproportional type governor in which position of the throttle valve isalmost wholly independent of centrifugal weight position. This has beenaccomplished by utilizing what may be termed a force type servo governormechanism in which centrifugal Weight force alone is converted intovalve travel, as distinguished from a travel type servo governormechanism in which centrifugal weight travel, resulting from a change inforce output, is converted into valve travel.

This invention is illustrated in FGURES l and 2 ofthe drawings in a fuelcontrol device of the so-called threedimensional cam type, which type ofcontrol is fully disclosed in my copending application Serial No.248,402, filed September 26, 1951. One of the problems encountered inthe use of such controls relates to excessive wear, over a period oftime, of the contoured three-dimensional acceleration cam which resultsfrom excessive spring loads and the like imposed on said cam by the camfollower during engine accelerations. My invention provides mechanismassociated with the governor for relieving any such excessive load onthe cam, thereby greatly increasing the useful life thereof.

One of the primary objects of this invention is to provide an improvedengine speed governor wherein a speed selecting force output is directlyconverted into a fuel now controlling travel.

Another object of this invention is to provide a force type servogovernor for engines which is not subject to certain inherentlimitations heretofore existent in direct acting and servo actuatedproportional type governors.

A further object of this invention is to provide cam load limiting meansin a combustion engine fuel control device.

Additional objects and advantages of this invention will become apparentto those skilled in the art in view of the following description takenin conjunction with the drawings, wherein;

FlGURE l is a sectional schematic view of a gas turbine engine and adiagrammatically illustrated .fuel control system connected thereto;

FIGURE 2 is a sectional schematic view of an engine' governor andassociated mechanism adapted to be used in the fuel control device ofFIGURE 1, in accordance with the invention; and

FIGURE 3 is a curve chart, illustrating the operational characteristicsof the governor shown in FIGURE 2.

Referring now to FGURE l, a gas turbine engine is generally indicated atiti and includes a series of annularly disposed combustion chambers llmounted in a casing having a header or air intake section l2, and acompressor i3, shown as of the axial flow type, whichis driven by meansof a turbine 14 through a shaft 15. Each of the combustion chambers isprovided witha burner nozzle 16 to which metered fuel is supplied underpressure by way of a conduit 17, fuel manifold 18 and individual fuellines 19. rfhe conduit i7 receives metered fuel from a fuel controldevice, generally indicated at 2t) in FIGURE l, which includes theapplicants governing mechanism as shown in FlGURE 2. A pump 22 suppliesfuel under pressure to fuel control 20 through a conduit 24, a portionof which fuel may be by-passed back to the pump inlet through a conduit26.

The fuel control 20 contains mechanism adapted to respond to compressorinlet temperature (Ta), as sensed by a temperature bulb 2S, compressorinlet pressure (Pa), picked up by a impact pressure pick up tube 30,compressor discharge pressure (Pc), picked up at a second impactpressure pick up tube 32, engine speed (N), which is transmitted to saidcontrol by means of a bevel gearing arrangement 34 and 36 and a governordrive shaft 38, and to the position of a pilots control lever 4t), whichis mounted as a rotatable shaft 48 in a control quadrant 50, and whichis connected to the fuel control device 20 by means of a link 42, alever 44 and a shaft 46.

Referring now to FIGURE 2, the governing mechanism is shown containedwithin a housing of the fuel control device 20, which receives fuel at apressure P1 from conduit 24 is aninlet passage 82 and an annular chamber84 formed between the housing and a fixed cylindrical sleeve member 86,Vand which discharges fuel to the metered fuel conduit 17 at a pressureP2 by way of a port SS, formed in the surface of a reciprocable androtatable hollow cylindrical metering valve member 9i? and adapted toVariably register with a port 92 formed in sleeve 86, a valve chamber94, valve ports 96, sleeve ports 98, an annular chamber 16@ and a fueloutlet passage 102.

The angular position of metering valve is at all times controlled as afunction of compressor discharge pressure by a geared rack member 104and a gear sector 106 tixed on an extension 108 of valve 90 and havingsplined gear teeth 110 in mesh with the gear teeth of rack 104. The rack104 is formed on a rod 105 which is tixedly secured to the movable endof an evacuated belvlows 111. The bellows 111 is mounted in a sealedchamber 113 which receives compressor discharge pressure Pc from theimpact pressure pick up tube 32 via a conduit 112. The bellows 111responds to the compressor discharge pressure Pc in chamber l113 androtates valve 90 -through rack 104 and sector 106 such that a givenangular -position of valve 90 is maintained for each value of compressordischarge pressure Pc.

The axial position of metering valve 90' within sleeve 86 is controlledeither by a contoured three-dimensional acceleration cam 114, which isadapted to cooperate with a cam follower and valve rod 116 and 118during an accelerationof the engine, or by all-speed governingmechanisrn contained within housing chamber 120 and connected to themetering valve by a power servo piston 122 and a walking beam 124. Thewalking beam 124 is adapted to be variously fulcrumed at a ball jointconnection 126 on a servo piston rod 128, at a pivot connection 130 to arod 132 of a cam load limiting piston 134, or at a ball joint connection136 on the cam follower rod 118, in a manner to be described. The axialposition of ,valve 98 is at all times determined by that mechanism whichdemands the least quantity of fuel, i.e. the acceleration cam and thegoverning mechanism are arranged in mutually overriding relation, ashereinafter described, so that that one which tends to fix lthe smallestarea at metering ports 88, 92 controls.

The acceleration cam 114 is mounted on a shaft 138 which is rotatablyand axially actuable as a function of certain engine operatingparameters such as engine speed and compressor inlet temperature,respectively. The shaft 138 carries a pinion 139 lixed secured thereto,said pinion being engaged with and rotated by a rack 141 formed on a rodxedly secured to a pitson 143.V The pistou 143 is responsive to a servopressure P5 which is controlled by a half ball servo valve 145. The halfball servo valve 145 is positioned as a function of engine speed byapivot lever 147 operatively connected between said half ball servovalve and the centrifugal weights 160. The shaft 138 is positionedaxially by a bellows 149 which has an operative connection with thetemperature bulb 28 lby means of a tube 151, the bellows and tube beinglled with suitable fluid or material responsive to temperature changesregistered by the bulb 28. The structural details and mode of operationof the above mentioned mechanism for axially and rotatably actuating theshaft 138 is conventional and will be easily understood by those skilledin the art. The acceleration fuel flow schedule may be controlled by thecam 114 and rack 104 to vary as a predetermined function of Pc, Ta andN, such that maximum allowable turbine inlet temperature issubstantially maintained throughout a predetermined portion of theacceleration schedule, and the phenomenon known as compressor surge orstall is not encountered. The angular and axial position controls forvalve 90 at all times cooperate to define a metering area 140 formed atthe portion of registry between ports 88 and 92. For example, ascompressor discharge pressure increases, rack 104 actuates gear sector106 to move valve 90 in a clockwise direction, as viewed from the topthereof, increasing dimension x of the metering port in proportion tothe increase in said pressure, and variation in any engine operatingparameter which effects a change in the axial position of metering Valve90 varies dimension y of port 140.

Preferably, a constant fuel pressure differential is at all timesmaintained across metering port 140 by a regulator valve means generallyshown at 153 and preferably of the type disclosed in U.S. Patent No.2,689,606, grantedA September 21, 1954, to Frank C. Mock and assigned tothe present assignee, whereby the iiow through said port is always apredetermined function of only those engine operating parameters whichcontrol the angular and axial positions of valve 90.

The governor mechanism contained within chamber connects the pilotcontrolled levers 40 and 44 to the power servo piston 122 by way of theshaft 46, a governor setting cam 142 mounted on shaft 46 for rotationtherewith and adapted to be axially actuable by compressor inletpressure and/ or temperature responsive mechanism, a cam follower rod144, a speed selecting governor spring 146 mounted between springretainers which abut the rod 144 and a servo valve lever 148, fulcrumedat 150, a half-ball type servo valve 152 connected to the lever 148 andcooperating with a discharge oriiice 154 in a servo pressure passage156, a governor feedback tension spring 158 resiliently connecting theservo piston rod 128 with the left end of servo lever 148, and a pair ofrotatable centrifugal weights 160 mounted on brackets 162 at pivots 164for rotation with a mounting plate 166 which is keyed to the governordrive shaft 38, said centrifugal weights having foot members 16S inabutment with a ange of a force transmitting rod 172, which in turnabuis a lever 174 pivoted at 176 for transmitting a moment of the forceoutput of weights 160 to servo lever 148 at a governor slope adjustingnut 178. The compressor inlet pressure responsive mechanism may take theform of an evacuated bellows 155 suitably mounted in a sealed chamber157 which receives compressor inlet pressure from impact pressure pickup tube 30 via a conduit 159. A rod 161 extends from the movable end ofbellows 155 into engagement with the shaft 46 such that a given axialposition of the cam 142 is maintained for each value of the compressorinlet pressure. The bellows 155 may be replaced by temperature sensingmechanism similar to `the afore-mentioned temperature sensing bulb 28,tube 151 and bellows 149 in which case the shaft 46 could be actuated asa function of compressor inlet temperature Ta. The compressor inletpressure and temperature re- .sponsive mechanism may be combined to forma conventional density sensitive apparatus, not shown, such that theshaft 46 is positioned as a function of compressor inlet pressure andtemperature.

The servo pressure (P5) passage 156 connects the P1 pressure chamber 84to chamber 120, which is connected to pump by-pass conduit 26 by apassage, not shown, at pump inlet pressure lo. A discharge pressureregulator valve in passage 156 is adapted to maintain a constantpressure in said passage upstream of a calibrated restriction 182, thepressure Ps beneath power piston 122 therefore varying solely as afunction of the area ratio between restriction 181. and orifice 154. Apower return spring 184 and fuel at. pump inlet pressure in a chamber186 opposes Ps pressure and spring 158 across piston 122.

A servo balance spring 188, adjustable by means of a screw 190, isutilized to act on lever 148 and 192 for the purpose of compensating forvariations in manufacturing tolerances between the designed rates ofsprings 146 and 158, and for insuring that said latter springs willsustain a pre-load even when the engine is at rest; this latter functioninsures that neither spring 146 nor 158 will ever be extended to a freeheight or no-load condition. If either of said springs were ever toreach a 11o-load condition they might become disconnected from theirrespective retaining means. The effective force output of the balancespring 188 on the servo system remains substantially constant,irrespective of variations in engine operating conditions, as the resultof an arrangement which effects a total range of movement of servo valve152 amounting to only a very few thousandths of an inch.

During all conditions of engine governing and equilibrium operation thefulcrum 130 of Walking beam 124 is maintained in the position shown by acam load limiting spring 196, which is contained in a cylindricalchamber 198 formed on one side of piston 134. The spring 196 normallymaintains piston 134 in abutment with a stop 200 formed in the housing8%, and the chamber 198 is vented to P pressure in chamber 1211 by anopening 202 in piston 134, a chamber 264, and an aperture 266 in stop2130.

Operation Referring now to FEGURE 3, sea level acceleration, governing,and steady state engine characteristics are qualitatively illustrated bythe curves 221i, 222. and 224, respectively, on the curve chart which isplotted on the coordinates of fuel ow in pounds per hour versus enginespeed in rpm. The basic contour of the characteristic seal levelacceleration curve 220 is fixed by the contour of the acceleration cam114, which is actuable as a function of certain engine operatingparameters, as hereinbefore described whereas the height or level ofsaid curve above the engine speed coordinate is primarily controlled bythe compressor discharge pressure responsive mechanism. The governorfuel cut-off curve 222 illustrates the operation of my force servo typeproportional governor from the acceleration curve to a selected speedpoint on the engine steady state operating curve. The steady state curve224 illustrates engine fuel iiow demand at all available engine speedsduring sea level operation.

Assume that the engine has been started and accelerated to the steadystate operating point a in the mid-speed range. In this condition ofoperation the pilots control lever 4t) will be positioned approximatelymid-way between the ends of quadrant Sti, in which position link andlever 42 and 44 position the governor setting cam 142 on shaft 46 so asto impose a speed selecting load on governor spring 146 through camfollower rod 144 which demands that engine operating speed existent atpoint a. In this condition of operation the half-ball servo Valve 152,being maintained in fixed position by an existent force balance on lever148, controls a servo pressure Ps in passage 156 which imposes a forceon servo piston 122; this force is balanced by the opposing forces ofthe governor feedback spring 158, the power return spring 1S4, and thepump inlet pressure in chamber 186, whereby the position of walking beam124 is iixed thereby controlling the axial position of metering valve 9%such that the area of metering port 149 controls that quantity of fuelflow to the nozzle 16 which is necessary to maintain engine speed as setat point a.

The forces acting on servo lever 148 in a direction which tends to moveservo valve 152 in an opening direction, i.e. in a direction which wouldresult in an accelerating fuel flow to the engine, consist of the momentforces of governor spring 146, feedback spring 15S, and the fuelpressure force on servo valve 152 at orifice 154, all acting aboutfulcrum 15G. These moment forces are opposed and balanced by the momentforce of the centrifugal weights 169, which varies as the square ofengine speed, and the substantially constant moment force of the servobalance spring 183. At any given speed, the engine driven centrifugalweights 161B` generate an effective force output on lever 14S which isequal to the Weight force output times the ratio of the lever armbetween rod 172 and fulcrum 176 to the lever arm between nut 17S andfulcrum 176. The force output of weights 160 is therefore diminished atlever 148 by the lever ratio factor, said factor being adjustable by nut173 to adjust the governor cut-on slope as will be hereinafterdescribed.

The design of the area of servo piston 122, of the lever ratio ofwalking beam 124 across fulcrum 131i?I between pivots 126 and 136, ofthe area relation between restriction 182 and orifice 154, and of therate of feedback spring 158, with a given configuration of meteringports 8S, 92 enables full governor cut-olir action to be effected at anyspeed with extremely small movement of servo light spring 196.

valve 152, the maximum movement of which will not exceed .004 or .005inch. This arrangement enables the governing mechanism to actuatemetering valve through its total range of movement with substantially nochange in the radius of rotation of governor weights 16?, whereby thegovernor mechanism inherently lends itself to a large degree of designversatility with respect to meeting the operating characteristics ofengines having widely different fuel requirements, inasmuch as meteringvalve 99 may be controlled throughout its axial travel rance with anegligible change in position of the weights 169. From this it is alsoapparent that a substantially constant force is imposed on lever 148 bythe balance spring 188, irrespective of variations in loading ongovernor spring 146 at different selected speeds.

Assume now that the pilot actuates control lever 40 in acounterclockwise direction to select, say, a maximum operating speed forthe engine, as denoted by point d on curve 224, and as illustrated bythe position of lever 40 in FIGURE l. As the pilot rotates lever 40 tothe indicated maximum speed position, the fuel control unit reactssubstantially instantaneously as follows: Governor setting cam 142 isrotated on shaft 46 to a position at which the cam rise imposes maximumcompression on governork spring 146 to select that speed at which thegovernor weight force and other forces acting on servo lever 143 will bein equilibrium, as illustrated at point d; servo lever 14, being nolonger in balance, rotates a minute amount in a clockwise direction toincrease the area ratio between orice 154 and restriction 182, therebyinstantaneously decreasing servo pressure Ps and unbalancing the forcesacross servo piston 122; the force differential across piston 122actuates the piston downwardly, and the walking beam 124 is rotatedabout fulcrum in a clockwise direction until cam follower 116 comes intoContact with acceleration cam 114, in which position the metering areahas increased to effect an increasein fuel ow from point a on curve 224to point b on curve 220.

The amount of compression imparted to governor spring 146 which is inexcess of that necessary to effect an acceleration to point g on curve224 results in a continued downward movement of piston 122, followingcontact of cam follower 116 with acceleration cam 114, about anewfulcrum 136, as pivot 130 and piston 134 move downwardly from thenormallyV fixed position thereof aga-inst spring 196 until piston 122reaches a position at which the decreased loadings on springs 134 and158 plus the 10W pressure in chamber 186 again balances the force ofpressure P5; the loading force imposed on the acceleration cam throughfollower 116 is thereby held to a relatively small amount, which resultsonly from the degree of compression imparted to the The increase of fuelflow from point a to point b results in an excess over that required torun the engine at the existing speed, and acceleration proceeds alongcurve 220, as determined by the contour of cam 114 which effects anopening movement of metering valve 90 in an axial direction; at the sametime compressor discharge pressure responsive rack 104 eects an yopeningrotational movement of valve 96. The combined axial and rotationalmovement of Valve 9G' results in a fuel flow versus speed characteristicsuch as is illustrated by the curve segment bc. As acceleration of theengine proceeds from point b, and the rate of opening movement of valve96 is determined by the rotating cam. 114, it is apparent that thefulcrum of walking beam 124 will shift from pivot 136 to pivot 126, asspring 196 actuates piston 134 and pivot 13@ upwardly until the pistonis again in contact with the stop 20G. During such upward movement ofpiston 134, beam 124 is rotated in a clockwise direction about pivot126, contact between follower 116 and the decreasing rise of cam 114being thereby positively maintained, while the engine is accelerating,with a cam loadspenen ing force which varies within chosen design limitsas a function of the rate of spring 196. It is apparent that selectionof a low rate cam loading spring will insure against exceesive loadsbeing placed on the cam 114 during acceleration of the engine, withresultant long cam life.

At the speed indicated at point c, the centrifugal Weights v160 havegenerated a force output which is suihcient to begin to overcome theforce moments of governor spring 145 and feedback spring 158, saidspring 158 being, at this time, in a relatively relaxed condition. Servovalve 152 therefore moves slightly upwardly to reduce the area ratiobetween orifice 154 and restriction `182, thereby producing an immediateincrease in pressure Ps which unbalances servo piston 122 in an upwarddirection, resulting in a counterclockwise rotation of walking beam 124about fulcrum 130 and a movement of follower 116 away from accelerationcam 114 to reduce the dimension y of metering port 140. As piston 122moves upwardly, feedback spring 158 elongates and produces an increasingmoment of force on servo lever 148 in the same direction as thatproduced by governor spring 146. This action results in continuedacceleration of the engine as fuel flow decreases along the governorbreak curve 222, inasmuch as the increasing force output of spring 158necessitates a proportional increase in engine speed, so that theeffective force output of weights 160 plus the substantially constantforce output of balance spring 188 may balance the effective forceoutputs of spring 146 and 158 at equilibrium operation. In other words,neglecting the substantially constant forces of springs 146 and 188, andalso the small hydraulic force acting on valve 152, the increasing loadon feedback spring 158 feeds into the governor mechanism a demandincrease in engine speed which is proportional to the decrease in fuelilow along the governor break curve 222. This proportional governingcharacteristic imparts a negative slope to the fuel cut-off curve whichis afunction of the rate of the feedback spring, and permits the engineto reach a stable equilibrium point of operation.

An unstable condition which is generally known as hunting in thegovernor art, would result if the feedback spring were not included inthe governor mechanism; i.e. without spring 158 a substantially verticalor isochronous governing characteristic, as illustrated by curve edf,would result due to the relatively constant force output of governorspring 146 at any given selected speed. Again, without spring 158 aslight variation in engine speed above or below that selected by thepilot would result in movement of servo valve 152 to cause potentiallymaximum movement of servo piston 122 and metering valve 90 in seeking acondition of equilibrium.

When the fuel flow required to run the engine is being metered at pointd, no accelerating engine torque exists, and the governing mechanism isin a state of equilibrium; i.e. the moments of forces acting on lever148 in a clockwise direction exactly balances the opposingcounterclockwise moments, and the positions of servo piston 122 andmetering valve 90 are fixed. If, for any reason, the engine should tendto increase or decrease speed from point d, as with a decrease orincrease in the density of the surrounding atmosphere, respectively,fuel now ould tend to vary along curve ,222 to reestablish equilibriumon the new engine operating curve.

With any given xed design rate of spring 153, the slope of the governorbreak curve may be manually adjusted as desired by nut 178, inwardadjustment on lever 174 effecting an increase in the slope of thegovernor cut-off curve as a result of the increased effective forceoutput of weights 160 with a given increase in engine r.p.m., andoutward movement of nut 178 on lever 174 effecting a decreased slope ofsaid curve.

The relative arrangement of parts, as shown in Fl"- URES l and 2,approximates that which would exist if an engine were being controlledby Ymy device to operate at point d. It should be remembered that thefulcrum of the walking beam 124 maintains a fixed position, as shown,throughout governor cut-off and equilibrium operation at any selectedspeed, the fulcrum of beam 124 shifting to pivot 136 only duringdownward motion of piston 134 against spring 195 following initialcontact of cam follower 116 with the acceleration cam, and that saidfulcrum shifts from pivot 136 to pivot 126 only during upward movementof piston 134 to the position indicated during an acceleration of theengine to the beginning of governor cut-off action.

A deceleration of the engine is effected by relaxing the loading ofspring 146 by counterclockwise movement ofpilots lever 4i), whichimbalances the forces acting on lever 14g and effects an upward movementof piston 122 until piston rod 123 contacts a deceleration stop 226; asbeam 124 rotates about fulcrum 130 in a counterclockwise direction tothe position determined by stop 226, the axial position of meteringvalve 90 and the y dimension of metering area 140 are xed. Fuel ilowimmediately decreases along the curve df, and the engine then begins todecelerate along the curve fh as metering area dimension x decreaseswith decreasing compressor discharge pressure. At point h the forceoutput of Weights has decreased to such an extent that spring 146 beginsto overcome said weight force output and move servo valve 152 slightlyopen to cause an opening movement of the metering valve 96, whichincreases fuel flow as the engine speed decreases along the proportionalgovernor break curve ha. At point a the control again reaches acondition of equilibrium.

From the above description, it is now apparent that I have provided aforce type governor servo mechanism having a built in proportionalgovernor break characteristic with means for adjusting the slope thereofas desired, plus means for minimizing the loading to which anacceleration cam is subject during an acceleration of the engine.

It will be apparent to those skilled in the art that various changes inthe structure and relative arrangement of parts may be made withoutdeparting from the scope of my invention.

I claim:

l. in a fuel feed and power control system for a gas turbine enginehaving a burner, a fuel conduit for conducting fuel to the burner, valvemeans for regulating the flow of fuel through said conduit, a movablemaximum flow stop operatively connected to said valve means for limitingthe rate of valve opening movement during an acceleration of the engine,and a force type servo governor mechanism operatively connected to saidvalve means for controlling the fiow regulating function of said Valvemeans as an inverse function of engine speed inciuding servo valvemeans, resilient means operatively connected to said servo valve meansfor imposing an engine speed selecting force thereon, the force outputof said resilient means being substantially constant during governorcutoff action to any given selected engine speed, an engine speedresponsive element operatively connected to said servo valve means fortransmitting a force thereto which opposes said speed selecting forceand which varies as a function of existing engine speed, the forceoutput of said speed responsive element varying substantially only withvariations in engine speed during governor cut-ofi action to a selectedspeed, and a yielding means operatively connecting said servo valvemeans to said governor valve means for transmitting a force to saidservo valve means which varies as a function of the position of saidgovernor valve means during governor cut-off action to a selectedVengine speed. i

2. In a fuel feed and power control system for a gas turbine enginehaving a burner, a fuel conduit for conducting fuel to the burner, valvemeans for regulating the iow of fuel through said conduit, a movablemaximum ow stop for limiting the rate of valve opening movement duringan acceleration of the engine, and engine speed governor mechanism forcontrolling the flow regulating fulcrum being shiftable to said iirstpivot means following the initiation of control of said valve means bysaid movable stop.

3. A fuel feed and power control system as claimed in claim 2 whereinsaid fulcrum is shiftable from said first pivot means to said thirdpivot means during valve controlling movement of said stop.

4. A fuel feed and power control system as claimed in claim 3 whereinsaid fulcrum is shiftabie from said third pivot means to said secondpivot means during actuation of said valve means away from said stop bysaid engine speed responsive means.

5. In a fuel feed and power control system for a gas turbine enginehaving a burner, a fuel conduit for conducting fuel to the burner, valvemeans for regulating the ow of fuel through said conduit, valve stopmeans operatively connected to said valve means during an accelerationof the engine, and engine speed governing means for controlling the owregulating position of said valve means as an inverse function of enginespeed during governor cut-off operation following an acceleration of theengine including a walking beam, first pivot means connecting said valvemeans to said beam, second pivot means operatively connecting yieldingmeans to said beam, and third pivot means operatively connecting enginespeed responsive means to said beam, said second pivot means beingadapted to function as a beam fulcrum during governor cut-off operation,and means for adjusting said engine speed responsive means to select anoperating speed for the engine, said fulcrum being shiftable to saidfirst pivot means following selection of a new engine operating speed bysaid adjusting means.

6. A fuel feed and power control system as claimed in claim 5 whereinsaid fulcrum is shiftable from said first pivot means to said thirdpivot means during an acceleration of the engine.

7. In a fuel feed and power control system for a gas turbine enginehaving a burner, a fuel conduit for conducting fuel to the burner, vaivemeans for regulating the ow of fuel through said conduit, a contouredacceleration cam adapted to be operatively connected to said valve meansduring an acceleration of the engine, and an engine speed responsivegovernor mechanism operatively connected to said valve means forcontrolling the flow regulating position of said valve means duringgovernor cut-olf and equilibrium operation of the engine, said lastmentioned operative connection including lever means having a movablefulcrum, said fulcrum being movable from a rst to a second positionalong said lever means l following actuation of said valve means into anoperative connection with said cam means.

8. A fuel feed and power control system as claimed in claim 7 whereinsaid fulcrum moves from said second position to a third positionWhenever the position of said valve means varies with the contour ofsaid cam.

9. An engine speed governor comprisingV governor valve means forcontrolling the flow of motive fluid to the engine, engine speedresponsive means operatively connected to said valve means forcontrolling the flow regulating position thereof as an inverse functionof engine speed, and means operatively connected to said speedresponsive means for selecting an operating speed for the engine, saidrst mentioned operative connection including a walking beam having afulcrum, rst pivot means operatively connected to Walking beam and saidvalve means, second pivot means operatively connected to said Walkingbeam and said engine speed responsive means, and third pivot meansoperatively connected to said walking beam intermediate said frst andsecond pivot means and supported by resilient means, said fulcrum beingshiftable between said first, second and third pivot means during anacceleration of ythe engine from a first to a second selected enginespeed.

10. In a fuel fed and power control system for a gas turbine enginehaving a burner, a fuel conduit for conducting fuel to the burner, valvemeans for regulating the ow of fuel through said conduit, a maximum flowstop adapted to be operatively connected to said valve means during anacceleration of the engine, engine speed responsive means operativelyconnected to said valve means for controlling the flow regulatingfunction thereof as an inverse function of engine speed, said operativeconnection including lever means connected to said engine speedresponsive means, means operatively connected to said speed responsivemeans for selecting an operating speed for the engine, said levermeanshaving a fulcrum, and resilient means operatively connected to saidfulcrum for maintaining a fixed position thereof during control of saidvalve means by said governor means, said resilient means being adaptedto permit a change in the position of said fulcrum during control ofsaid valve means by said maximum flow stop, following the initiation ofan acceleration of the engine by said speed selecting means for limitingthe force loading on said stop.

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